High R1+R2

[lurch]

I have a customer who recently had a test an an inspect on his new house. the report showed a high r1+r2 reading on the shed suply. I have checked it out and cant find anything obvious that would suggest why the reading is high on the cpc. however I cant get to a JB that is concealed behind a newly installed kitchen which seems to be the only obvious place the fault can be (the JB apparently is an adaptable box chnaging the t&e to swa, which I reckon is probaly a loose gland on the swa/adaptable box). My suggestion is to provide a earth rod at the shed. the circuit is RCD protected. . . . . thoughts please.

Lurch

 

[Mr Mark Sparks]

how high is r1r2 because the armour on the swa should be earthed could the loose connection eventually fail leaving it un earthed

i wonder if you could earth the armour back of the new stake?
not sure this is ok though

 

[lurch]

how high is r1r2 because the armour on the swa should be earthed could the loose connection eventually fail leaving it un earthed

i wonder if you could earth the armour back of the new stake?
not sure this is ok though

I havent got the test sheet avaialbel but recall it being around 300ohms. the armour will pick up the earth at the adaptable box from the t&e assuming thi shas been done properly. Yes, if I put a stake in I will earth the armour. ps the supply to the property is tns.

 

[acat]

Doubt you will get away with that part of the property would be tns the other tt giving you an unequal potential at the property.

Junction box should be accessible at all times and if you work on the circuit you take responsibility for it

Hope that helps

Chris

 

[lurch]

Doubt you will get away with that part of the property would be tns the other tt giving you an unequal potential at the property.
Chris, could you confirm why this would not be acceptable.

Junction box should be accessible at all times and if you work on the circuit you take responsibility for it

Hope that helps

Chris

And agreed the JB should be accessible at all times. Unfortunately I did not carry out the original instal of the shed feed or the kitchen install. I am trying best to sort an issue with least disruption possible.

Thx again

 

[acat]

Never heard of it being acceptable and I cant find anything in 17th edition that would allow it you either has a tncs, tns or tt not a mixture.

As for the junction box if you touch that circuit you assume responsibility for the entire circuit best to ring the NICEIC or whoever you are registered with to see if noting that on your certificate would suffice.

Chris

 

[Spudnik]

I cant see anything wrong with TT in a shed/garage if the property is another system.

Providing the SWA is installed correctly.

Done it a few times.

 

[acat]

Thanks Jason we live and learn


Chris

 

[Spudnik]

Chris,

This is often done if there are metal services in a garage for example, and saves running a separate 10mm earth bonding cable back to the house MET.

Of course, this is all if the supply cable to the shed/garage is not adequate.

 

[lurch]

thanks for al your replies........ tis now done.

rgds Lurch

 

[pushrod]

Just wondering Lurch did you check that the cpc was completely responsible for the high R1+R2 and can you or anyone explain how you now test R1+R2 with a TT system or do you not have to?

 

[Guest123]

can you or anyone explain how you now test R1+R2 with a TT system or do you not have to?

same as you would any other system, link line and cpc of required circuit at DB and measure at furthest point on circuit if radial, if ring link P1 and E2, P2 and E1 and measure at each socket outlet recording the highest as R1+R2.

 

[pushrod]

same as you would any other system, link line and cpc of required circuit at DB and measure at furthest point on circuit if radial, if ring link P1 and E2, P2 and E1 and measure at each socket outlet recording the highest as R1+R2.

Probably just me being dim, but was thinking about the previous scenario in the shed that is now earthing through an earth spike - would there have to now be a new small CU in the shed ? If not the Phase and cpc are going to be nowhere near each other to link